The removal of various polar gaseous polutants such as SO.sub.2 from the gaseous effluent of industrial smoke stacks is a project of top priority among environmentalists. Industrial sources of SO.sub.2 can be divided into two types, those with rich effluent (2,500-500 ppm SO.sub.2) such as smelting plants, and those with lean effluent (500-100ppm) such as electric power plants. The latter are far more numerous and by far the leading SO.sub.2 pollution source. The reduction of SO.sub.2 effluent concentration to the 500 ppm level is a fairly developed process which can be done at close to break-even economics. The reduction to below the 100 ppm level, which is presently being studied internationally due to proposed legal limits in that range, has proved to be a far less economically solvable problem.
The numerous approaches by which the problem has been attacked may be divided into basic types. First, processes that were successful in cleaning highly concentrated streams were applied to the cleaning of dilute streams. Process equipment sizing and reaction kenetics made these processes either unworkable or very expensive. In another type of system, the pollutants were absorbed or chemisorbed onto a substrate which was then discarded; this method simply changed the form of the pollution and when it was sold on the market it generally destroyed the value of the commodity in the market. In neither case was the process economically feasible. Still another type of process involved adsorption or sorption of the pollutants on a substrate and the subsequent regeneration of the pollutant by heat. Parenthetically, it might be a good idea at this point, to explain what is meant by the terms "absorption" or "chemisorption" versus "adsorption". In the first instance, the pollutant and the substrate react chemically, irreversibly forming a new substance. In the latter, the two materials are held together by surface attraction and simple heat can drive them apart. The term "sorb" or "sorption" refers to an instance in which generally reversible attraction is present but the exact nature of the surface attraction phenomena is not presumed. Returning to the sorption methods, most of the work done in this area has involved attempts at carrying existing adsorption processes into the pollution area. They are generally not suited for hot, "dirty" streams or low concentrations and have received little attention from public and private funding agencies. Thus, the various systems for SO.sub.2 pollution abatement are, at present, either uneconomical, uneffective, or not developed to a practical stage.
These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a sorption system which divides a hot fluid stream containing a medium concentration of an impurity into a stream of rich concentration and a cool stream of weak concentration.
Another object of this invention is the provision of a sorption system which is suitable for extracting impurities from the effluent of a fossil fuel burning furnace.
A further object of the present invention is the provision of a sorption system which is adaptable to any separation involving adsorbents, particularly octane benefication of hydrocarbon fuels.
It is another object of the instant invention to provide a sorption system which is simple and inexpensive.
With the foregoing and other objects in view, which will appear as the description proceeds, the invention resides in the combination and arrangement of steps and the details of the system and process hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.